Texture paint does not render in cycles or is very light
I believe the Material Preview mode will show you the "pure" image texture without performing the full shader material computing.

On that note, I notice that you are trying to mix the image texture which seems already quite subtle in variations, with a similar color (the one on the bottom input on the Mix node) using the noise texture. It does not seem surprising that the final render result is very faint.

Try a more vibrant color in the mix node to see the difference. Also, a good practice is to use a Color Ramp on the output of the Noise texture to control the  contrast (moving controls left and right.)